Supplemental lubrication pressurized by component or reservoir rotation

TECHNICAL FIELD

This disclosure relates generally to a drive system, and more particularly, though not exclusively, to lubricated bearings, gears, and other components within gearboxes that require continued operation after primary lubrication system failure.

BACKGROUND

In high speed rotating machinery, such as gearboxes, transmissions, aircraft engines, or other rotating parts, containing bearings, shafts, and gears, lubrication by pressurization of the lubricant which flows through jetted orifii directly to the component requiring lubrication is common. External pressure may be applied to the lubricant by using, for example, an oil pump which draws oil from a sump and directs it toward the component. However, situations may occur, for example when the oil pump fails or when oil leaks from the system, such that the primary pressurized lubricant system experiences a severe pressure drop which may cause the components to seize or get damaged, which may sometimes be catastrophic.

It would therefore be desirable and advantageous to provide supplemental lubrication in the event of a catastrophic failure of the primary pressurized lubrication system.

SUMMARY

This disclosure relates generally to the lubrication of rotating components, such as shaft bearings and gears. According to one aspect of the present disclosure, a supplemental lubricant reservoir is arranged inside the shaft and rotates at shaft speed. The reservoir is filled with a lubricant of desired viscosity from the primary pressurized lubrication system, with the lubricant being forced by the centrifugal force generated by the shaft rotation toward the bearing, for example an inner bearing ring, arranged outside the shaft through a discharge channel, such as a metered orifice. The lubricant in the supplemental lubricant reservoir is continuously replenished from the primary pressurized lubrication system during normal operation of the rotating system. When the primary pressurized lubrication system fails, lubrication will continue to be provided by the lubricant in the supplemental lubricant reservoir while the rotation speed of the shaft is controllably decreased and ultimately stopped following an emergency shutdown of the rotating system. According to another aspect of the present disclosure, a supplemental lubricant reservoir is arranged outside a first shaft (for example a drive shaft) of a gearbox and rotates at shaft speed. A second shaft (for example a driven shaft) is connected to the first shaft by a gear which requires lubrication. The reservoir is filled with lubricant of desired viscosity from the primary pressurized lubrication system, with the lubricant being forced toward the gear by the centrifugal force generated by the rotation of the first shaft through a discharge channel, such as a metered orifice, for example in form of a mist. The lubricant in the supplemental lubricant reservoir is continuously replenished from the primary pressurized lubrication system during normal operation of the rotating system. When the primary pressurized lubrication system fails, lubrication of the gears will continue to be provided by the lubricant in the supplemental lubricant reservoir while the rotation speed or power requirements of the first shaft is controllably decreased following an emergency shutdown of the rotating system to a safe rotation speed where continuous lubrication is no longer required and ultimately stopped. It will be understood that the roles of the first and second shaft may be reversed.

According to yet another aspect of the present disclosure, lubrication systems with supplemental rotating lubricant reservoirs are utilized in or around the rotor mast and in a gearbox of the tail rotor of a rotorcraft, such as a helicopter, to prevent the rotating rotor mast and the gears in the gearbox from failure to transmit torque or seize, thus allowing a controlled landing of the rotorcraft in the event of a failure of the pressurized primary lubrication system.

BRIEF DESCRIPTION OF THE DRAWINGS

<figref idref="DRAWINGS">FIG. 1</figref> illustrates schematically an example rotating shaft with an external pressurized primary lubrication system for a bearing and a supplemental rotating lubricant reservoir in accordance with certain embodiments;

<figref idref="DRAWINGS">FIG. 2</figref> illustrates schematically an example embodiment of a rotating shaft with a supplemental rotating lubricant reservoir fed by an oil jet during normal operation in accordance with certain embodiments;

<figref idref="DRAWINGS">FIG. 3</figref> illustrates schematically another example embodiment of a rotating shaft with a supplemental rotating lubricant reservoir fed by the primary lubrication system during normal operation in accordance with certain embodiments;

<figref idref="DRAWINGS">FIG. 4</figref> illustrates schematically an example embodiment of a gearbox with a supplemental rotating lubricant reservoir arranged externally on a rotating shaft in accordance with certain embodiments, and

<figref idref="DRAWINGS">FIG. 5</figref> illustrates an example rotorcraft in accordance with certain embodiments.

DETAILED DESCRIPTION

The following disclosure describes various illustrative embodiments and examples for implementing the features and functionality of the present disclosure. While particular components, arrangements, and/or features are described below in connection with various example embodiments, these are merely examples used to simplify the present disclosure and are not intended to be limiting. It will of course be appreciated that in the development of any actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, including compliance with system, business, and/or legal constraints, which may vary from one implementation to another. Moreover, it will be appreciated that, while such a development effort might be complex and time-consuming, it would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

In this specification, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of the present disclosure, the devices, components, members, apparatuses, etc. described herein may be positioned in any desired orientation. Thus, the use of terms such as “above,” “below,” “upper,” “lower,” “spaced-apart” or other similar terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components, should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the components described herein may be oriented in any desired direction.

Further, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Example embodiments that may be used to implement the features and functionality of this disclosure will now be described with more particular reference to the attached FIGURES.

<figref idref="DRAWINGS">FIG. 1</figref> illustrates an example embodiment of a system <b>100</b> with a shaft <b>112</b> supported for rotation in a housing <b>102</b> by at least one bearing <b>114</b>. The bearing <b>114</b> has an inner race <b>114</b><i>a </i>connected to the shaft <b>112</b> and an outer race <b>114</b><i>b </i>that may be connected to the housing <b>102</b>. The housing may be closed off at the bottom, wherein a lubricant <b>108</b>, such as oil, is collected at the bottom forming an oil pan or a sump <b>109</b>. In the illustrated example, the bearing <b>114</b> may be supplied with the pressurized lubricant <b>108</b> by an oil pump <b>104</b> through a supply line <b>106</b>, wherein the inlet of pump <b>104</b> draws oil from the oil pan <b>110</b>. It will be understood that the pump <b>104</b> may be arranged inside or outside the housing <b>102</b>. Throughout the specification, the terms lubricant and oil as well as sump and oil pan, respectively, may be used interchangeably.

<figref idref="DRAWINGS">FIG. 1</figref> furthermore shows a supplemental lubricant reservoir <b>116</b> disposed inside the shaft <b>112</b> and co-rotating with the shaft <b>112</b>. Lubricant <b>108</b> is continuously supplied to the supplemental lubricant reservoir <b>116</b> from the sump <b>110</b>, in the illustrated example system <b>100</b> through a supplemental feed line <b>118</b> which keeps the supplemental lubricant reservoir <b>116</b> filled during normal operation, i.e. when lubricant is conveyed to the primary lubrication system by pump <b>104</b>. Pressure generated by the centrifugal force as a result of the shaft rotation indicated by arrow <b>122</b> continuously conveys a small, optionally metered amount of lubricant from the supplemental rotating lubricant reservoir <b>116</b> through an orifice <b>120</b> to the bearing <b>114</b>, preferably to an inner bearing race <b>114</b><i>a. </i>

Oil pumps may have different designs. For example, twin gear pumps (also called external pumps) may be mounted inside the oil pan near the bottom section of the shaft <b>112</b> and use a pair of intermeshing gears to pump oil. The pump gears turn in opposite directions. This traps oil between the gear teeth and carries it around the outside of each gear from the pickup tube inlet to the pump outlet. The tight clearances between the gears prevent the oil from flowing backwards to the inlet. Another type of oil pump is a rotor pump (also called “gerotor” pump) that has an inner gear that turns inside an outer rotor. The inner gear has one less lobe than the outer rotor. The inner gear is also mounted slightly off-center to the outer rotor which forces the outer rotor to spin at about 80% of the speed of the inner gear. This creates a bellows-like pumping action that pulls oil from the inlet port and pushes it towards the outlet port. Close tolerances are required for good pumping efficiency. This type of pump may also be located in the sump. Another type of oil pump is a so-called cover oil pump usually located in or on a cover of the rotating system <b>100</b>. When this type of pump becomes worn, it is hence not always necessary to replace the entire cover assembly, provided the pump housing inside the cover is not worn or damaged. A new drive gear can be mounted on the shaft and a new rotor installed in the cover to rejuvenate the pump without complete disassembly. These types of oil pumps are frequently used in automotive engines and other drive aggregates, so that there design and operation will not be described further.

Upon rotation of shaft <b>112</b> the generated centrifugal force creates a pressure on lubricant <b>108</b> within reservoir <b>116</b> as follows:

<maths id="MATH-US-00001" num="00001"><math overflow="scroll"><mrow><mrow><mrow><mi>Δ</mi><mo>⁢</mo><mstyle><mspace width="0.3em" height="0.3ex" /></mstyle><mo>⁢</mo><mi>P</mi></mrow><mo>=</mo><mrow><mfrac><mi>ρ</mi><mrow><mn>2</mn><mo>⁢</mo><mi>g</mi></mrow></mfrac><mo>⁢</mo><mrow><mo>(</mo><mrow><msubsup><mi>R</mi><mn>0</mn><mn>2</mn></msubsup><mo>-</mo><msubsup><mi>R</mi><mn>1</mn><mn>2</mn></msubsup></mrow><mo>)</mo></mrow><mo>*</mo><msup><mi>ω</mi><mn>2</mn></msup></mrow></mrow><mo>,</mo></mrow></math></maths>

wherein ΔP=outlet pressure difference between pressure at orifice <b>120</b> and lubricant supply pressure, <ul id="ul0001" list-style="none"><li id="ul0001-0001" num="0000"><ul id="ul0002" list-style="none"><li id="ul0002-0001" num="0021">ρ=lubricant density,</li><li id="ul0002-0002" num="0022">g=gravitational constant (981 cm/sec²),</li><li id="ul0002-0003" num="0023">R₀=outlet radius at orifice <b>120</b>,</li><li id="ul0002-0004" num="0024">R₁=inner radius at lubricant supply pressure,</li><li id="ul0002-0005" num="0025">ω=shaft rotation speed (rad/sec).</li></ul></li></ul>

When the pressurized primary lubricant supply through line <b>106</b> fails, the lubricant supply pressure drops to zero so that the outlet pressure at orifice <b>120</b> is produced only by the rotation of shaft <b>112</b>. Failure of the primary lubricant system may be detected by an (unillustrated) oil pressure sensor, causing an emergency shutdown of the shaft rotation by rapidly reducing the shaft rotation speed or power requirement of <b>122</b>. As a result of a speed change, the flow rate through orifice <b>120</b> decreases during this time which also gradually decreases the pressure ΔP while still supplying an adequate quantity of lubricant to the components that require continuous lubrication, such as shaft bearing <b>114</b>. It will be understood that the oil capacity of the supplemental lubricant reservoir and the shutdown of the shaft rotation need to be carefully matched so that the bearing <b>114</b> does not run dry.

<figref idref="DRAWINGS">FIG. 2</figref> shows an embodiment according to the disclosure of a system <b>200</b> with a rotating mast <b>212</b> of an otherwise unillustrated rotorcraft. The mast <b>212</b> may support, for example, the main rotor of the rotorcraft. Shown in <figref idref="DRAWINGS">FIG. 2</figref> are only those components that are part of the bearing, gear and lubrication system. As described above with reference to <figref idref="DRAWINGS">FIG. 1</figref>, the system <b>200</b> includes a pressurized primary lubrication system with an oil pan or sump <b>208</b> and a supplemental rotating lubrication system with a supplemental reservoir <b>216</b> co-rotating with the mast <b>212</b>. The mast is supported for rotation in a housing (not explicitly shown) by bearings <b>214</b><i>a</i>, <b>214</b><i>b</i>, which require lubrication while the mast <b>212</b> rotates. Also schematically illustrated is a planetary gear <b>215</b> which may be used to transmit a rotary motion to the mast <b>212</b>.

During normal operation, all bearings and gears are lubricated by a lubricant fed from the pressurized primary lubrication system. Additionally, an oil injection tube <b>218</b> with an inlet connected to the pressurized primary lubricant supply and an outlet in form of an orifice, shooting an oil jet <b>219</b> upwards through the hollow mast <b>212</b> to strike the inside of the hollow mast <b>212</b> above the entrance opening <b>217</b> of the supplemental reservoir <b>216</b>. As a result of the centrifugal force generated by the rotation of the mast <b>212</b>, the lubricant then flows along the inside wall of the mast <b>212</b> and drips down into the reservoir <b>216</b>. The oil surface at the entrance opening <b>217</b> forms a concave meniscus when the mast <b>212</b> rotates. Pressure generated by the centrifugal force as a result of the shaft rotation continuously conveys a small, optionally metered amount of lubricant from the supplemental lubricant reservoir <b>216</b> through an orifice <b>220</b> to the exemplary planetary gear <b>215</b>. This ensures that the lubricant in the supplemental reservoir is continuously recycled or replenished during normal operation, i.e. when lubrication is provided by the pressurized primary lubrication system.

When the pressurized primary lubricant supply fails, hydraulic pressure at the orifice <b>220</b> is produced only by the rotation of mast <b>212</b>. This ensures that a sufficient quantity of lubricant continues to flow to the example planetary drive <b>215</b>. Additional unillustrated orifices and flow passages may be arranged to feed lubricant to the bearings <b>214</b><i>a</i>, <b>214</b><i>b</i>, and other locations requiring continuous lubrication.

Turning now to <figref idref="DRAWINGS">FIG. 3</figref>, <figref idref="DRAWINGS">FIG. 3</figref> shows a different arrangement of a rotating supplemental reservoir <b>316</b> which co-rotates with a lower shaft <b>312</b> operatively connected to the planetary gear <b>215</b>. The lower shaft <b>312</b> may for example have a rotation speed different from that of mast <b>212</b>. Metered orifices <b>320</b><i>a</i>, <b>320</b><i>b </i>feed lubricant to, for example, the planetary gear <b>215</b>, the bearing <b>214</b><i>c </i>and other gears housed in the part of an unillustrated housing enclosing shaft <b>312</b>. It will be understood that both embodiments of the supplemental reservoirs <b>216</b> and <b>316</b> may be used severally or in combination to supply lubricant to essential components that require continuous lubrication until all rotating components come to a complete stop in the event of an emergency shutdown or at least attain a safe rotation speed where external lubrication may no longer be necessary.

Another embodiment of a supplemental rotating reservoir is illustrated in <figref idref="DRAWINGS">FIG. 4</figref>, wherein the supplemental rotating reservoir <b>416</b> co-rotating with a first rotating shaft <b>412</b><i>a </i>is arranged outside the first rotating shaft <b>412</b><i>a</i>. The first rotating shaft <b>412</b><i>a </i>may be for example a drive shaft and a second shaft <b>412</b><i>b </i>a driven shaft. Both shafts <b>412</b><i>a</i>, <b>412</b><i>b </i>are housed inside a gearbox <b>410</b> and connected by a gear <b>415</b>. Shaft <b>412</b><i>a </i>may be supported for rotation by bearings <b>414</b><i>a</i>, <b>414</b><i>b</i>, while shaft <b>412</b><i>b </i>may be supported for rotation by bearings <b>414</b><i>c</i>, <b>414</b><i>d</i>. The supplemental rotating reservoir <b>416</b> is constantly fed with optionally filtered oil from the primary gearbox lubrication system. The oil in the reservoir <b>416</b> continuously flows through one or more metered openings <b>420</b> (only one opening is shown) and is replenished until the primary gearbox lubrication system fails and no longer has the pressure to feed the reservoir <b>416</b>. In this case, an oil mist that lubricates all components requiring continuous lubrication is the fed from the supplemental rotating reservoir into gearbox <b>410</b> through the metered orifice(s) due to pressure generated by the centrifugal force caused by the rotation of shaft <b>412</b><i>a </i>and reservoir <b>416</b>.

<figref idref="DRAWINGS">FIG. 5</figref> illustrates an example embodiment of a rotorcraft <b>500</b>, in which the systems described above with reference to <figref idref="DRAWINGS">FIGS. 1 to 4</figref> may be employed. The illustrated example portrays a side view of the rotorcraft <b>500</b>. The rotorcraft <b>500</b> includes a rotor system <b>502</b> with a plurality of rotor blades <b>504</b>. The pitch of each rotor blade <b>504</b> can be managed or adjusted in order to selectively control direction, thrust, and lift of rotorcraft <b>500</b>. The rotorcraft <b>500</b> further includes a fuselage <b>506</b>, a tail rotor or an anti-torque system <b>508</b>, an empennage <b>510</b>, and a tail structure <b>512</b>. In the illustrated embodiment, the tail structure <b>512</b> may also include a horizontal stabilizer. Torque is supplied to the rotor system <b>502</b> and to the anti-torque system <b>508</b> using at least one engine (not shown) which may be housed under a variety of cowling assemblies <b>514</b> configured to cover components of the rotorcraft and to reduce aerodynamic drag. The rotor system may be supported by a mast <b>212</b> of the type illustrated in <figref idref="DRAWINGS">FIGS. 2 and 3</figref>, respectively, which employs the lubrication system with a supplemental rotating lubricant reservoir, as described above. The tail rotor or an anti-torque system <b>508</b> may be driven, for example, by the drive shaft <b>412</b><i>a </i>and the driven shaft <b>412</b><i>b </i>operatively connected by an interposed gearbox <b>410</b> of the type illustrated in <figref idref="DRAWINGS">FIG. 4</figref>, which also includes a supplemental rotating lubricant reservoir.

It should be appreciated that rotorcraft <b>500</b> of <figref idref="DRAWINGS">FIG. 5</figref> is merely illustrative of a variety of aircraft and machinery that can be used to implement embodiments of the present disclosure. Aircraft implementations may also include, for example, fixed wing airplanes, hybrid aircraft, tiltrotor aircrafts, unmanned aircraft, gyrocopters, a variety of helicopter configurations, and drones, among other examples. Moreover, it should be appreciated that even though aircrafts are particularly well suited to implement embodiments of the present disclosure, the described embodiments can also be implemented using non-aircraft vehicles and devices.

The diagrams in the FIGURES illustrate the architecture, functionality, and operation of possible implementations of various embodiments of the present disclosure. Although several embodiments have been illustrated and described in detail, numerous other changes, substitutions, variations, alterations, and/or modifications are possible without departing from the spirit and scope of the present invention, as defined by the appended claims. The particular embodiments described herein are illustrative only, and may be modified and practiced in different but equivalent manners, as would be apparent to those of ordinary skill in the art having the benefit of the teachings herein. Those of ordinary skill in the art would appreciate that the present disclosure may be readily used as a basis for designing or modifying other embodiments for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. For example, certain embodiments may be implemented using more, less, and/or other components than those described herein. Moreover, in certain embodiments, some components may be implemented separately, consolidated into one or more integrated components, and/or omitted.

Although certain embodiments have been described with reference to a components found in a rotorcraft, the embodiments are not limited to rotorcrafts but may also be used in other types of machinery that uses rotating parts requiring continuous lubrication during their normal operation.

Numerous other changes, substitutions, variations, alterations, and modifications may be ascertained to one of ordinary skill in the art and it is intended that the present disclosure encompass all such changes, substitutions, variations, alterations, and modifications as falling within the scope of the appended claims.